The treemap

Each row in the SharePoint list/document library is a rectangle on the graph. The size of the rectangle can represent a numeric property of the item.

When rendering by grouping data

Each unique value in the grouped value is a rectangle . The size of the rectangle can represent the Minimum/Maximum/Average/Median/Sum/First/Last/Row Count/Unique value of this unique value.

Negative values

By design, the rectangle graph cannot represent negative numbers. In case of negative number in the data, the visualizer will convert to its absolute number. For example, the value -100 will be converted to 100, then graphed.